Here's the Autolite 4100 four-barrel with automatic choke and anti-stall dashpot for automatic transmission applications. The 4100 has vacuum-actuated secondaries for a smooth trip into power mode when the accelerator pedal is floored. Had emission laws not become strict a decade later, the 2100 and 4100 would have remained in production until the end of carbureted Mustangs in the mid-1980s.